There are a whopping eleven different
characters who you can choose to romance in Mass Effect 3, each of whom will
have different requirements and requests if you opt to pursue their hearts.
Some, like Specialist Traynor, will be simple one night affairs that can be
completed far before the end of the game, while others, such as Liara, you will
have to wait until the end of the game to truly see through. This guide will
cover each character, the requirements for winning their hearts, and which
genders they are available to. First up is…

Ashley Williams:

Available Genders: Only male Shepard

Requirements:

This one is a bit specific, so pay
close attention. First of all, in order to romance Ashley she will have to be,
you know, living. It goes without saying, but you will have to have chosen
Ashley over Kaiden in the first Mass Effect. It will not matter whether or not
you romanced her in that first game, though. You will simply have to visit her
several times in the Huerta Memorial Hospital, starting right after she is
admitted following the Priority: Mars mission, again towards the middle of Act
1 (when you receive her first email,) and a final time at the very end (when
you receive the last email, after Priority: Palaven.) Buying her a gift from
the little gift shop vending machine in the Huerta Memorial Hospital lobby will
improve your chances of romancing her later. Purchase the Collected Alfred
Tennyson item to receive the best response; she will be shocked that you
remembered this little detail from the first game. If you dated her in the
first Mass Effect, you can romance her again earlier than you would be able to
otherwise. After you go through this process, Ashley will ask to meet with you
in the Presidium Commons area of the Citadel following the Cerberus attack.
Meet with her, and she will either ask you to date her (this only happens if
you made the exact right dialogue choices when speaking with her earlier,) or
you can ask her yourself if you hit the mark close enough.

Diana Allers:

Available Genders: Both male and female Shepards

Requirements:

Meet up with Diana during your
very first visit to the Citadel, after Ashley or Kaiden has been hospitalized
on Mars. She will be standing around in the lobby. Invite her to join you on
the Normandy to document your actions. You will really only have to perform a
couple of specific requirements after this. Diana isn’t exactly the most
demanding of lovers. She will, however, demand that you either kill off the
quarians or unite the warring races in the Priority: Rannoch mission. You
should also head to the Engineering Deck early on to find her hanging out here,
and speak with her. Otherwise, if you intend to romance Diana, just remember to
invite her up to your private quarters for interviews when you receive emails
saying that you can do so. The first of these will come after the Citadel is
raided, and the second after Rannoch. Give her good interviews (use the
Persuade option when available) and make passes at her to get her love scene.

Garrus:

Available Genders: Only female Shepard

Requirements:

First, you have to have romanced
Garrus in Mass Effect 2 in order to continue it here. Talk to Garrus when you
first recruit him into your party to continue the relationship. After this,
just speak to him after Priority: Tuchanka, and again on the Citadel when you
receive the email inviting you to hang out. Commit to a serious relationship
during this conversation. Note that you can break your commitment if you say
during the first conversation that you want to stay with Garrus only to romance
someone else over the course of the game. This will lead to a romance blooming
between Garrus and Tali.

Jack

Available Genders: Only male Shepard

Requirements:

This one also requires you to have
started the relationship in Mass Effect 2. After that, you will have to
complete the Grissom Academy mission that you will receive from Specialist
Traynor early on. When you encounter Jack during this mission, you should act
in a generally agreeable fashion. This means using the more Paragon-leaning
responses, not the Renegade ones. After the mission is over, a Paragon
interrupt prompt will appear. Hit LT to complete the prompt. After this, the romance
is similar to the others. Wait for an invitation to meet on the Citadel, and
find Jack to speak with her in Purgatory. Tell her that you still want her, and
you will complete this romance.

Kaiden Alenko:

Available Genders: Both male and female Shepards

Requirements:

The requirements for this romance
differ just a little depending on whether you are playing a male or female
character, but largely it will be the same either way. Naturally, you will have
to have chosen to let Kaiden live over Ashley in the first Mass Effect. When
Kaiden is hospitalized after the Mars mission, visit him in the hospital right
away. This little section right here is the key differentiator for male players
who want to romance Kaiden, as the entire future of the romance hinges on one
little moment that many people may miss. Before heading into the patient ward
to visit Kaiden, examine the gift shop console in the middle of the hospital
lobby. Purchase the TM-88 Peruvian Whiskey. Female players should do this as
well, but male players be warned: if you don’t purchase the whiskey, you will
have no other opportunities to romance Kaiden. Deliver the whiskey to him in
his hospital room and generally be positive about his recovery and accepting
about your history together. After the Priority: Palaven mission, visit him
again, and again be positive. Gain his trust, and have him join your party
after the Citadel attack. Keep up with him on the Normandy and he will soon
offer to meet with you on the Citadel, in the Presidium Commons. Meet him there
and either accept his offer to date, or bring it up yourself. Note that you do
not have to have romanced Kaiden in the first Mass Effect to do so successfully
here.

Garrus is the one who should be available for both genders, not Kaidan. They should have decided to base the which current squaddie becomes bi on the amount of people who wanted to have a s/s romance with him rather than deciding on going with the one who had the least amount of people screaming "he's not gay!"

Garrus had more people who wanted a s/s romance with him and also more people who squawked that it would ruin the character and that he wasn't gay. Making Kaidan the s/s option rather than Garrus is pandering to the homophobes IMO

I just want to report an error with this guide. If you are male, and want to romance Kaidan, you DON'T have to give him the whiskey in the beginning. I was worried myself because i forgot to give him the whiskey. But it was possible to romance him anyway. So, the whiskey is NOT the trigger. Just wanted to confirm what a lot of people have been wondering.